For example, a step-down type of DC-DC converter is used in information equipment. Such a DC-DC converter employs a switching power supply using a switch. A buck type power supply circuit is used in a case where ground in input and that in output are commonly used (see Non-Patent Document 1). A power supply circuit having a snubber circuit is used in order to suppress power consumed at the time of turning on/off of a main switch (see Non-Patent Document 1 and Non-Patent Document 2).
[Non-Patent Document 1] John G Kassakian, Principles of power electronics, ADDISON-WESLEY PUBLISHING COMPANY, 1992, pp 674-687
[Non-Patent Document 2] IEEE Transaction on Power Electronics, Vol. 11, Issue. 5, 1996, pp 710-722